The present invention relates to an outdoor unit of an air conditioner of an engine heat pump type, in which an engine is used for driving compressors of the air conditioner.
In a conventional air conditioner of a heat pump type, particularly for home use, an electric motor has been used to drive a compressor for compressing a cooling (heating) medium such as Freon (Trade Mark).
However, such air conditioners, which have been broadly used, have such a problem that electric power consumption is large, and, especially in a heating operation in a cold season, the electric consumption is very large because a heating efficiency of the heat pump is low.
In order to overcome the above problem, Japanese laid open publication No. 56-71773 has disclosed a heat pump air conditioner having a high energy efficiency, which includes two compressors driven by an engine, one of which is designated to have a compression ration smaller than that of the other so as to minimize the power consumption.
However, the above heat pump air conditioner can not disadvantageously perform defrosting operation during the heating operation in which a waste heat of the engine for driving the compressors is used as a heat source.
Further, in the conventional construction, since there is a difference between the pressures of the cooling medium in a heat exchanger for the outside air and a heat reclaimer for the engine, the two compressors are required, and thus, two accumulators for catching the liquid cooling medium are required for the compressors, respectively. Therefore, an accumulator system has been expensive.
Further, when the heat is excessively supplied from a cooling water to the cooling medium for utilizing the waste heat of the engine, the cooling water becomes relatively cold so that the engine may be over-cooled, which results in problems such as low durability of the engine, unstable combustion and large power loss. Moreover, in the over-cool condition, a large gap is formed between a piston and a cylinder liner in the engine, resulting in a large blowby gas, and, especially in a gas engine, resulting in such a problem that a large quantity of water is mixed into a lubricating oil.
Further, in the conventional construction, a complicated check valve arrangement is used in a piping arrangement.
Accordingly, it is an object of the invention to provide an improved outdoor unit of an air conditioner of an engine heat pump type, overcoming above-noted disadvantages, in which compressors can be driven by an engine with a small power consumption and a defrosting operation can be performed during a heating operation by utilizing a waste heat of the engine.
It is also an object of the invention to provide an improved structure, overcoming the above noted disadvantages relating to the accumulator, over-cooling and the check valve arrangement.